This invention is directed to ion injectors and more specifically to injectors for generating negative ions.
A number of injectors are used for producing negative ions. Typically such injectors include a source of positive ions that produces a positive ion beam, separate electromagnets for analyzing and focusing the beam, and a charge conversion apparatus that transfers electrons to the positive ions thereby to convert the positive ions to negative ions. More particularly, such charge conversion apparatus vaporizes some substance, such as lithium, to produce a vapor through which the positive ion beam must pass. As the positive ion beam passes through the vapor, electrons transfer to the ions thereby converting them to negative ions to produce a negative ion beam.
Generally, these injectors include separate deflecting and focusing electromagnets and electrostatic lenses that discretely deflect the ion beam thereby to analyze the beam and that focus the beam at a focal spot in the charge conversion apparatus. The negative ion beam from the conversion apparatus passes through another focusing lens into an accelerating section along an injection path.
As known, the ion beam in such injectors travels in a vacuum. More specifically, such injectors are constructed with vacuum chambers and vacuum pumps to maintain the vacuum. Positive ion sources generally use a gas so that the vacuum pumps must overcome the gas that is admitted to the system from the source. In order to minimize leakage and other sources of gases, prior injectors position the electromagnets or electrostatic lenses externally to the vacuum chamber. This increases the magnetic gap of such devices over that which is really needed to pass the ion beam, and the increase in magnetic gap requires that the electromagnet or electrostatic lenses be bulkier, become more expensive to manufacture due to the increased sizes and concomitant increase in power supply requirements, and, due to increased power requirements, more expensive to operate. In many new applications, however, such characteristics have become unacceptable.
Therefore, it is an object of this invention to provide an improved injector of negative ions.
Another object of this invention is to provide an improved injector of negative ions that is inexpensive to produce.
Still another object of this invention is to provide an improved injector of negative ions that is compact.
Yet another object of this invention is to provide an improved injector of negative ions that is reliable in operation.